Guest starspirit Posted January 29, 2007 Share Posted January 29, 2007 When I last used the van for a 20 mile run about a week ago both batteries showed a no load 12.95 volts just after I turned the engine off. I removed both fuses to isolate both from each other and the rest of the van's circuitry. One battery now shows 12.58 volts and the other 12.51 volts with no load. Does anyone know whether this drop is normal please or whether I have two batteries slowly dying? Thanks Link to comment Share on other sites More sharing options...
Mel E Posted January 29, 2007 Share Posted January 29, 2007 It is completely normal. All batteries show a higher 'no load' voltage immediately after charge. If you keep the meter connected, you can watch the voltage drop gradually. Link to comment Share on other sites More sharing options...
Brambles Posted January 29, 2007 Share Posted January 29, 2007 It is caused by surface charge on the plates which after charging slowly dissipates. I believe it can take a few hours to completely settle. Basically it is charge left on the lead plates which behave like a capacitor. There is not enough voltage in the charge to actually charge the batteries. Jon. Link to comment Share on other sites More sharing options...
Guest starspirit Posted January 29, 2007 Share Posted January 29, 2007 I was always under the impression that to be fully charged a battery would need to show above 12.8 volts and below 12.5 it was either in need of a recharge or starting to fail? Link to comment Share on other sites More sharing options...
Philman Posted January 29, 2007 Share Posted January 29, 2007 Hi starspirit, I think that a charged battery should not drop below 12.6v off load. The slight differences that you read on your meter may be within tolerance to its spec. To remain really accurate digital meters need to be calibrated about once a year but this is generally not that practical unless you have access to a calibration lab. Anyway I doubt if your batteries would have received a full charge after a 20 mile run. Of course it depends on the state of charge before the run. It would be best if you could charge them with a suitable charger for a day or so and then let them stand for about 12 hours. If you then check the terminal voltage and it has again fallen below the 12.6v level you may need to think about new batteries some time in the future. I assume you've checked electrolyte levels and topped up if necessary. Phil. Link to comment Share on other sites More sharing options...
Guest starspirit Posted January 29, 2007 Share Posted January 29, 2007 Thanks Phil. The van did 200 miles the week before and the batteries showed nearly 12.97 volts at rest afterwards, and yes the electrolyte levels have been checked and are OK. Link to comment Share on other sites More sharing options...
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